Make rustc_log doc test runnable

Cargo.lock

@@ -4080,6 +4080,7 @@ name = "rustc_log"
 version = "0.0.0"
 dependencies = [
  "atty",
+ "rustc_span",
  "tracing",
  "tracing-subscriber",
  "tracing-tree",

compiler/rustc_log/Cargo.toml

@@ -3,14 +3,14 @@ name = "rustc_log"
 version = "0.0.0"
 edition = "2021"
 
-[lib]
-doctest = false
-
 [dependencies]
 atty = "0.2"
 tracing = "0.1.28"
 tracing-subscriber = { version = "0.3.3", default-features = false, features = ["fmt", "env-filter", "smallvec", "parking_lot", "ansi"] }
 tracing-tree = "0.2.0"
 
+[dev-dependencies]
+rustc_span = { path = "../rustc_span" }
+
 [features]
 max_level_info = ['tracing/max_level_info']

compiler/rustc_log/src/lib.rs

@@ -12,7 +12,7 @@
 //! rustc_span = { path = "../rust/compiler/rustc_span" }
 //! ```
 //!
-//! ```ignore
+//! ```
 //! fn main() {
 //!     rustc_log::init_rustc_env_logger().unwrap();
 //!